The present invention relates to improvements in an automatic transmission for an automotive vehicle, and more particularly to an automatic transmission which is imporved in structure and performance.
U.S. Pat. No. 3,581,858 discloses a conventional automatic transmission in which a clutch unit is arranged such that a cancel chamber is disposed to be opposite to an apply chamber relative to a piston for changing an operating condition of a cltuch. The cancel chamber is formed such that a pressure receiving surface is different from that of the apply chamber. This arrangement is not sufficient to actuate a piston pushing force due to centrifugal force pressure in the apply chamber by that in the cancel chamber.